How does loading multiple drivers on a channel affect required voltage limiting?

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Riflefeet
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How does loading multiple drivers on a channel affect required voltage limiting?

#1 Post by Riflefeet »

So currently I'm running eminence 3015lf 8ohms drivers on a single channel meaning that when I test the voltage to set my limiters properly I use a speakon cable with open wires at one end, and run full strength signal through the mixer/processors/amp into the cable and test the wires with my VOM and make sure the voltage doesn't exceed 55v, giving me a 5v headroom before I reach the limit of what the drivers can handle.

if I were to try to put say, two, or even three drivers per channel how would this affect my voltage output and where would I place my VOM to be sure all drivers are getting equal voltage? my current knowledge would tell me that by wiring them all in parallel (wiring the second speakon jack on the plate as a parallel thru jack) that all of them would have the same exact electrical properties giving me a resistance of 2ohms across all three. Based on V = I * R I get a voltage rating of 60v limit for 8ohms, but 15v limit for 2ohms. So I would assume that when I'm setting up the rig to run 3 drivers per channel I can test my voltage in the exact same way that I do currently except that my voltage limit would now be 15v instead of 60v. Am I correct or missing something here?

The second part of this is that Ive just upgraded to crown amps which allow me to set the voltage limit within the amp itself rather than what I have to do currently which is set a dB limit within the dbx driverack pa+ which adds an element of guess work and trust in the amps to consistently output power (which my old cheap inuke8000s did not do). So if I'm going to put 3 drivers per channel wired together via the parallel thru jacks on this new crown amp, I'm assuming that if I set my voltage limit to 14v within the amp's settings I'm going to be ensuring my system is working to its full potential while also protected from getting blown out.

Any input/clarifications/corrections are greatly appreciated!

CoronaOperator
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Re: How does loading multiple drivers on a channel affect required voltage limiting?

#2 Post by CoronaOperator »

Wiring in parallel using speakons is no different than using one of these:
Image

You don't adjust the voltage from the wall when you plug more stuff in do you? Your voltage that you limit to stays the same, no adjustment nesessary. Just like the above example however, the more stuff you plug in the more current flows from the amp. Thats where the extra power comes from. If you keep plugging stuff in, eventually too much current flows (impedance too low) and the amp shuts itself off to protect itself. The power bar above does the same thing with its built in breaker.
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Riflefeet
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Re: How does loading multiple drivers on a channel affect required voltage limiting?

#3 Post by Riflefeet »

Even though the resistance of the circuit is changing the voltage doesn't though? That's where I'm getting hung up.

CoronaOperator
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Re: How does loading multiple drivers on a channel affect required voltage limiting?

#4 Post by CoronaOperator »

Just as the voltage from your wall outlet stays the same regardless of what is plugged in, so does the amplifier outputs. What changes is the current flow. P=IV, where P= power, I = current flow, V= voltage. Plug 2 subs in, the voltage stays the same, the current doubles therefore the power from the amp doubles. Each sub gets the same power as if it was by itself because the resistance will divide the current.

Another way to visualize it is consider plugging a 120 watt light bulb into the above power bar. If your voltage is 120 v at the outlet, the bulb will draw 1 amp of current. Now plug in another 120 watt bulb. It too draws 1 amp of current at 120v. However both bulbs together now draw 2 amps from the power bar, 1 amp to each.
Built:
17" width 10" driver Autotuba
2 x 29" width dual Lab12 Tuba60
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Riflefeet
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Re: How does loading multiple drivers on a channel affect required voltage limiting?

#5 Post by Riflefeet »

ok I'm following you there, but the root of my question is that by wiring the drivers into parallel, I drop their overall resistance. In doing so does this change the voltage at which they could be blown out?

I'm guessing the answer in now based on your analogy but just want to be sure.

Ryan A
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Re: How does loading multiple drivers on a channel affect required voltage limiting?

#6 Post by Ryan A »

Riflefeet wrote:ok I'm following you there, but the root of my question is that by wiring the drivers into parallel, I drop their overall resistance. In doing so does this change the voltage at which they could be blown out?

I'm guessing the answer in now based on your analogy but just want to be sure.
Each driver will have their own same resistance regardless of how many other drivers are wired to it, and the voltage also stays the same if they are wired in parallel.

The only thing that changes is the total load (impedance) presented to the amplifier.

CoronaOperator
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Re: How does loading multiple drivers on a channel affect required voltage limiting?

#7 Post by CoronaOperator »

Riflefeet wrote:by wiring the drivers into parallel, I drop their overall resistance. In doing so does this change the voltage at which they could be blown out?
What Ryan said, the individual subs resistance doesn't change, only the total circuit resistance that the amplifier sees changes because there is more paths for the electricity to flow.
Built:
17" width 10" driver Autotuba
2 x 29" width dual Lab12 Tuba60
6 x DR250 2510/asd1001
In progress:
2 x DR250 2510/asd1001
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Bill Fitzmaurice
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Re: How does loading multiple drivers on a channel affect required voltage limiting?

#8 Post by Bill Fitzmaurice »

With parallel loads all drivers get the same voltage. They only split the voltage when in series.

Riflefeet
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Re: How does loading multiple drivers on a channel affect required voltage limiting?

#9 Post by Riflefeet »

Bill Fitzmaurice wrote:With parallel loads all drivers get the same voltage. They only split the voltage when in series.
Thanks for the responses everyone. For reference, if they were wired in series what would the voltage limits need to be set at in my scenario?

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Bill Fitzmaurice
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Re: How does loading multiple drivers on a channel affect required voltage limiting?

#10 Post by Bill Fitzmaurice »

Riflefeet wrote: if they were wired in series what would the voltage limits need to be set at in my scenario?
Add them.

Grant Bunter
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Re: How does loading multiple drivers on a channel affect required voltage limiting?

#11 Post by Grant Bunter »

Riflefeet wrote: that all of them would have the same exact electrical properties giving me a resistance of 2ohms across all three.
^This isn't right either.

Three x 8 ohm drivers in parallel on one channel = 2.66 Ohms.
4 x 8 ohm drivers in parallel on one channel is 2 ohms...
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escapemcp
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Re: How does loading multiple drivers on a channel affect required voltage limiting?

#12 Post by escapemcp »

^ v. common mistake though, although it's a nice one to realize that you are not loading your amp as much as you previously thought :)

Riflefeet
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Re: How does loading multiple drivers on a channel affect required voltage limiting?

#13 Post by Riflefeet »

Grant Bunter wrote:
Riflefeet wrote: that all of them would have the same exact electrical properties giving me a resistance of 2ohms across all three.
^This isn't right either.

Three x 8 ohm drivers in parallel on one channel = 2.66 Ohms.
4 x 8 ohm drivers in parallel on one channel is 2 ohms...
Whats your formula for that? I was taught (incorrectly apparently) that when you wire in parallel you split resistance in half and double resistance when in series.

Bruce Weldy
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Re: How does loading multiple drivers on a channel affect required voltage limiting?

#14 Post by Bruce Weldy »

Riflefeet wrote:
Grant Bunter wrote:
Riflefeet wrote: that all of them would have the same exact electrical properties giving me a resistance of 2ohms across all three.
^This isn't right either.

Three x 8 ohm drivers in parallel on one channel = 2.66 Ohms.
4 x 8 ohm drivers in parallel on one channel is 2 ohms...
Whats your formula for that? I was taught (incorrectly apparently) that when you wire in parallel you split resistance in half and double resistance when in series.
That works fine in pairs....but, you said three.....that requires the math to be done.

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CoronaOperator
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Re: How does loading multiple drivers on a channel affect required voltage limiting?

#15 Post by CoronaOperator »

Parallel resistance:

Image

for series resistance, just add them up
Built:
17" width 10" driver Autotuba
2 x 29" width dual Lab12 Tuba60
6 x DR250 2510/asd1001
In progress:
2 x DR250 2510/asd1001
For best results, point the loud end of the array towards the audience

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